Gastrulation Flashcards
At least half of all embryos are spontaneously aborted due to ___. Approximately __ of live births suffer from congenital defects. These results in personal suffering & huge costs to medical care systems.
developmental defects; 4%
Understanding developmental processes will ultimately lead to preventative strategies.
yup!
Embryonic cells divide about every ___ hours
16-24. Reductive division.
As the morula divides, some cells find themselves on the inside. These cells begin to express different genes including ____. ___ is an important marker of __ stem cells
Oct4; Oct4; pluripotent
As the blastula forms, the cells separate into 2 populations - the ___ & ___ layer
inner cell mass & trophoblast layer
Initially the ICM is an ____ of cells.
unorganized cluster of cells
The cells of ICM then separate into 2 layers the ___ & ___. Together, these 2 layers comprise the ___
epiblast & hypoblast; embryonic disk
How many days after fertilization does the ICM form 2 layers?
6-7 days - around time of implantation
After how many days after fertilization does the ICM cells express Oct4?
about 5 days after fertilization
The epiblast cells are high ___ in appearance. All cells of embryo itself will arise from the ___ layer
columnar; epiblast
What does the hypoblast form?
the supporting layer; forms yolk sac wall
The epiblast separates into 2 layers to form the ___. Only epiblast cells in contact with __ will form embryonic tissues.
amniotic cavity; hypoblast
The amniotic membrane is an ___ tissue. The amniotic fluid in the cavity protects the embryo
extraembyonic tissue
How many days after fertilization does the epiblast separate?
9 days after fertilization
From 7-14 days, the embryo undergoes rapid ___
cell division
The disk changes from roughly circular to ___, broader at __ end.
ovoid; cranial end
By 16 days the disk is approximately __mm x ___mm in size
1x1.5mm
Despite the undifferentiated appearance of the embryonic disk, a number of signaling events have already occurred. These will later distinguish specific regions of the embryo
primitive streak forms
How many cells are present in the mature human body?
1cm^3 = 10^9 cells
What is gastrulation?
process by which 3 embryonic germ layers are formed. Ectoderm, mestoderm & endoderm
Through physical movements of gastrulation, original epiblast tissue is divided into 3 different ___
tissue layers
Gastrulation commences about __ days after fertilization
14
The primitive streak is first visible at the ___ end & then extends more ___
caudal; cranially
The streak marks the position where epiblast cells have migrated towards the ___ & then ___. These migratory cells are called ____. ___ is a rather general term for loosely associated & migratory cells.
midline & then ingressed; mesenchyme; mesenchyme
This is an example of EMT (epithelial to mesenchymal transition - metastasis?)
Epiblast becomes the ___ & the migratory cells displacing the hypoblast becomes the ___
skin - ectoderm
gut - mesoderm
What are the migratory cells falling towards the hypoblast?
because cell loses cell-cell adhesion & therefore drops down & displaces the hypoblast
The first cells to ingres insert into hypoblast layer & displace it. These cells will form the embryonic __
endoderm
From top to bottom, what are the layers?
epiblast (future ectoderm), mesenchyme (future mesoderm) & hypoblast (future endoderm)
The mesoderm cells migrate both ___ & ____ until they occupy almost* the entire middle layer of the embryo
laterally & cranially
What is the future mouth & future anus called?
oral membrane & cloacal membrane
The oral & cloacal membrane will not contain ___
mesoderm
What is a notochord? It is also the center for ___ (by GF) to adjacent tissues. The notochord is later incorporated into the ___. The final remamnant of the notochord is the ____ of the intervertebral disk.
transient embryonic structure that acts as temporary spine for embryo
signaling by GF to adjacent tissues
backbone
nucleus pulplosis
Humans are in what phylum?
chordata - chords!!
As gastrulation proceeds the primitive streak regresses ___. It lays down more ___ as it regresses. The streak disappears by about day ___. If the streak cells don’t disappear, they may give rise to highly invasive class of tumors =
caudally; notochord; 30; sacral teratoma!
What is ectoderm, mesoderm & endoderm?
Ectoderm - outer layer of skin (epidermis) & neural tissues
Mesoderm - skeletal & smooth muscle, heart & blood vessels, blood, bones, dermis of skin. Supporting tissue b/w skin & gut tube
Endoderm - visceral organs including gut tube, bladder, liver, pancreas & lungs
Cells in the ICM are ___. They can develop into ____ different type of cell in the body. This has been confirmed many times with experimental animals.
totipotent; EVERY
It is now possible to grow human ICM cells indefinitely in culture. They’re called ___
human ES cells (hESCs)
In addition to GF, the culture medium contains # of factors that inhibit differentiation
What is iPS cells?
induced pluripotent cells
